1). Field of the Invention
This invention relates generally to a method of substrate processing, and more specifically to a method of photoresist removal.
2). Discussion of Related Art
Integrated circuits are manufactured on silicon and other semiconductor substrates by forming a multitude of semiconductor devices such as transistors, diodes, capacitors, and other devices on the substrate, and subsequently interconnecting these devices with metal lines and contacts. In conventional aluminum-based metalization techniques, a layer of aluminum is deposited and subsequently patterned to leave aluminum metal components with trenches between them. The trenches are then filled with dielectric material. For emerging copper-based metalization techniques, of which there are a number of variations, a layer of dielectric material is deposited, a pattern is etched into the dielectric, typically vias or trenches, and the metal components, usually copper, are electroplated or deposited.
In contrast to conventional metalization techniques, where silicon dioxide, (SiO2) is the standard dielectric with a nominal k-value of 4, advanced copper-based metalization schemes require low-k dielectric materials to alleviate the increased interconnect capacitance, which occurs when conventional methods are applied to smaller feature sizes. The increased capacitance leads to resistance-capacitance time delays which affect the overall processing speed of the integrated circuit.
In copper-based metalization processes, the dielectric layer is patterned by coating a photoresist layer on the dielectric layer, patterning the photoresist utilizing photolithography, and then using the photoresist layer as a mask to etch the pattern into the dielectric layer. The remaining photoresist and etch residue must then be removed or “stripped” utilizing an additional process. For conventional photoresist removal, an oxygen-based plasma is used. Because the photoresist layer is primarily an organic-based polymer, it oxidizes readily at elevated temperatures when treated with plasma through a mechanism similar to combustion of hydrocarbons in the presence of oxygen.